Diethyleneglycol ester based plasticizer composition and polyvinyl chloride resin using the same

ABSTRACT

The present invention relates to a diethylene glycol ester based plasticizer composition comprising at least two diethylene glycol ester compounds. The diethylene glycol ester based plasticizer composition of the present invention offers superior tensile strength, elongation, transfer resistance, hardness, transparency, adhesivity, and compatibility with resin, when used for a plasticizer of a polyvinyl chloride resin, without releasing environmental hormones. Thus, it can be used for a polyvinyl chloride resin of a warp film.

TECHNICAL FIELD

The present invention relates to a diethyleneglycol ester basedplasticizer composition, and more particularly to a diethyleneglycolester based plasticizer composition which can be used as plasticizer ofa polyvinyl chloride (PVC) resin.

BACKGROUND ART

The plasticizer added to a polyvinyl chloride resin or other polymerresins is an essential additive offering the polymer resin physicalproperties and capabilities such as processability, flexibility,electrical insulation, adhesivity, etc. Conventionally, phthalates,adipates, etc. have been typically used as plasticizer. The most widelyused plasticizers are di-2-ethylhexylphthalate (DEHP) anddi-2-ethylhexylalipate (DEHA). These plasticizers are used as standardsfor evaluating other plasticizers.

DISCLOSURE OF INVENTION

Technical Problem

However, the Environmental Protection Agency (EPA) of the U.S. and theNational Institute of Health Sciences of Japan have classifiedphthalates and adipates as environmental hormone materials.

Thus, development of a plasticizer comprising neither phthalate noradipate is required. U.S. Pat. No. 5,746,783 discloses a diesel fueladditive comprising a di-ethyleneglycol ester based compound, whichcomprises neither phthalate structure nor adipate structure and reducesnitrogen oxide exhausted from diesel engine.

A polyvinyl chloride resin is prepared from vinyl chloride monomers andother monomers copolymerizable with the vinyl chloride monomers. Byadding such additives as a plasticizer, a stabilizer, a filler, apigment, etc., the resin can be imbued with a variety of processingproperties.

The polyvinyl chloride resin is used for numerous applications includingpipes, cables, artificial leather, wallpaper, gloves, toys, wrap films,etc.

Particularly, the polyvinyl chloride resin used for a wrap film forpacking foods requires good tensile strength, hardness, elongationcapable of wrapping well packing manufactures, transparency capable ofseeing well with the naked eye foods, adhesivity after foods packing,transfer resistance, and compatibility with other resins.

Technical Solution

It is an aspect of the present invention to provide a diethylene glycolester compound for a plasticizer not releasing environmental hormones.

It is another aspect of the present invention to provide a diethyleneglycol ester based plasticizer composition useful for a plasticizer of apolyvinyl chloride resin comprising a diethylene glycol ester compound.

It is still another aspect of the present invention to provide apolyvinyl chloride resin for a wrap film having superior tensilestrength, elongation, hardness, transfer resistance, transparency, andadhesivity using the diethylene glycol ester based plasticizercomposition.

In order to attain the aspects, the present invention provides adiethylene glycol ester compound for a plasticizer represented byFormula 1-1 below:R₁OCO—(CH₂)₂—O—(CH₂)₂—OCOR₂  (1-1)

wherein R₁ is a phenyl group and R₂ is an alkyl group having 3 to 12carbon atoms.

The present invention also provides a diethylene glycol ester basedplasticizer composition comprising the diethylene glycol ester compoundrepresented by Formula 1-1.

The composition further comprises a diethylene glycol ester compoundrepresented by Formula 1-2 below; and a diethylene glycol ester compoundrepresented by Formula 1-3 below.R₃ OCO—(CH₂)₂—O—(CH₂)₂—OCOR₄  (1-2)

(wherein each of R₃ and R₄ is an alkyl group having 3 to 12 carbonatoms.)R₅OCO—(CH₂)₂—O—(CH₂)₂—OCOR₆  (1-3)

(wherein each of R₅ and R₆ is a phenyl group.)

More preferably, the plasticizer composition of the present inventioncomprises:

(a) 10 to 80 wt % of the diethylene glycol ester compound represented byFormula 1-1;

(b) 5 to 80 wt % of the diethylene glycol ester compound represented byFormula 1-2; and

(c) 5 to 60 wt % of the diethylene glycol ester compound represented byFormula 1-3.

The present invention also provides a method of preparing a diethyleneglycol ester based plasticizer composition by esterifiying 10 to 40 wt %of diethylene glycol, 20 to 70 wt % of 2-ethylhexanoic acid, 10 to 60 wt% of benzoic acid 1 to 10 wt % of xylene,

The present invention also provides a polyvinyl chloride resin preparedusing the diethylene glycol ester based plasticizer composition.

Advantageous Effects

As described above, the diethylene glycol ester based plasticizercomposition of the present invention improves tensile strength,elongation, transfer resistance, hardness, transparency, adhesivity,and/or compatibility of a polyvinyl chloride resin without generatingenvironmental hormones, when employed as the plasticizer of the resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a gas chromatography mass spectrometer (GC-MS) fordiethylene glycol ester based plasticizer composition of Example 1according to the present invention.

FIG. 2 shows a gas chromatography mass spectrometer (GC-MS) fordiethylene glycol ester based plasticizer composition of Example 2according to the present invention.

FIG. 3 shows a gas chromatography mass spectrometer (GC-MS) fordiethylene glycol ester based plasticizer composition of Example 3according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention is described in more detail.

The present invention is characterized by a plasticizer composition notcomprising phthalate or adipate, which are known as environmentalhormone materials and having superior tensile strength, elongation,hardness, transfer resistance, transparency and adhesivity, therebybeing useful for a polyvinyl chloride resin for a wrap film for packingfoods.

Preferably, the diethylene glycol ester based plasticizer composition ofthe present invention comprises at least two selected from the groupconsisting of diethylene glycol ester compounds represented by Formula 1below.R₇OCO—(CH₂)₂—O—(CH₂)₂—OCOR₈  (1)

wherein each of R₇ and R₈ is a phenyl group or an alkyl group having 3to 12 carbon atoms.

A wrap film used for packing foods should have superior tensilestrength, hardness, transfer resistance, transparency, elongation, andadhesivity. A plasticizer is added to the resin formed the foundation ofthe wrap film to offer such physical properties. The present inventionuses the compound represented by Formula 1 as plasticizer.

However, all of above physical properties cannot be satisfied only withthe compound represented by Formula 1. To be specific, the compound ofFormula 1 is 2-ethylhexanoic acid 2-2-(2-ethylhexanoyloxy)-ethoxy-ethylester synthesized from di-ethylglycol and 2-ethylhexanoic acid, orbenzoic acid 2-2-(benzoyloxy)-ethoxy-ethyl ester synthesized fromdiethylglycol and benzoic acid. However, the compounds of Formula 1 areused more as lubricant than as plasticizer, because they are notsufficiently compatible with polyvinyl chloride resin. And,2-ethylhexanoic acid 3-(2-ethylhexanoyloxy)-2,2-dimethylpropyl estersynthesized from neopentylglycol and 2-ethylhexanoic acid as othercompound of Formula 1 is insufficient for a wrap film because of highhardness and low transparency and elongation. Also, although2-ethylhexanoic acid [2-2-(2-ethylhexanoyloxy)-ethoxyethoxy]-ethyl estersynthesized from triethylene glycol and 2 ethylhexanoic acid hassuperior processability, it is disadvantageous in such physicalproperties as elongation, adhesivity, transparency, etc.

However, if two or more diethylene glycol ester compounds selected fromthe compounds represented by Formula 1 are used in differentproportions, plasticizers with different physical properties areobtained.

The plasticizer composition of the present invention offers superiortensile strength, elongation, hardness, transfer resistance,transparency, and adhesivity and has superior processability includingcompatibility with polyvinyl chloride resin by using two or morediethylene glycol ester compounds selected from the compoundsrepresented by Formula 1.

According to the method of preparing the diethylene glycol ester basedplasticizer composition of the present invention, at least two compoundsselected from the compounds represented by Formula 1, preferably threediethylene glycol ester compounds, are produced.

Of such compounds represented by Formula 1, the present invention ischaracterized by a diethylene glycol ester compound having the structureof Formula 1-1 below:R₁OCO—(CH₂)₂—O—(CH₂)₂—OCOR₂  (1-1)

wherein R₁ is a phenyl group and R₂ is an alkyl group having 3 to 12carbon atoms.

Because the compound represented by Formula 1-1 is the most preferablein terms of stability, a plasticizer composition comprising it hassuperior physical properties as plasticizer of a polyvinyl chlorideresin.

Accordingly, the present invention is characterized by a plasticizercomposition of a polyvinyl chloride resin comprising the diethyleneglycol ester compound represented by Formula 1-1.

Preferably, the composition of the present invention comprises thediethylene glycol ester compounds represented by Formulas 1-2 and 1-3below as the compound represented by Formula 1.R₃OCO—(CH₂)₂—O—(CH₂)₂—OCOR₄  (1-2)

wherein each of R₅ and R₆ is an alkyl group having 3 to 12 carbon atoms.R₅OCO—(CH₂)₂—O—(CH₂)₂—OCOR₆  (1-3)

wherein each of R₅ and R₆ is a phenyl group.

Preferably, the plasticizer composition of the present inventioncomprises:

(a) 10 to 80 wt % of the diethylene glycol ester compound represented byFormula 1-1;

(b) 5 to 80 wt % of the diethylene glycol ester compound represented byFormula 1-2; and

(c) 5 to 60 wt % of the diethylene glycol ester compound represented byFormula 1-3.

Preferably, (a) the compound represented by Formula 1-1 is benzoic acid2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester.

And, preferably, (b) the compound represented by Formula 1-2 is2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester.

And, preferably, (c) the compound represented by Formula 1-3 is benzoicacid 2-{2-(benzoyloxy)-ethoxy}-ethyl ester.

As a preferred embodiment of the present invention, the diethyleneglycol ester based plasticizer composition may comprise 10 to 80 wt % ofbenzoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester; 5 to 80 wt %of 2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester;and 5 to 60 wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy}-ethyl ester.

More preferably, the diethylene glycol ester based plasticizercomposition of the present invention comprises 30 to 60 wt % of benzoicacid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester; 10 to 60 wt % of2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester; and5 to 50 wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy}-ethyl ester.

Most preferably, the composition of the present invention comprises thecompounds (a), (b), and (c) at a proportion of 40:40:20 based on weight.

Hereinafter, the preparing method of the diethylene glycol ester basedplasticizer composition of the present invention is described in moredetail.

(a) The benzoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester maybe synthesized from diethylene glycol, 2-ethylhexanoic acid and benzoicacid by esterification.

(b) The 2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethylester may be synthesized from diethylene glycol and 2-ethylhexanoic acidby esterification.

And, (c) the benzoic acid 2-{2-(benzoyloxy)-ethoxy}-ethyl ester may besynthesized from diethylene glycol and benzoic acid by esterification.

To sum up, the diethylene glycol ester based plasticizer composition ofthe present invention may be prepared from diethylene glycol, benzoicacid, and 2-ethylhexanoic acid. In addition, other additives may beused.

In a preferred embodiment of the present invention, the diethyleneglycol ester plasticizer composition is prepared as follows.

10 to 40 wt % of diethylene glycol, 20 to 70 wt % of 2-ethylhexanoicacid, 10 to 60 wt % of benzoic acid, 1 to 10 wt % of xylene asentrainer, and 0.05 to 1 wt % of tetra-isopropyl titanate as catalyst,are put in a flask equipped with a stirrer and a condenser. Thetemperature of the flask is raised to 220° C. and esterification isperformed for 4 to 10 hours. After the esterification is over, theunreacted acid is removed with a vacuum pump and the remaining acid isneutralized with 5 to 15 wt % of sodium hydroxide.

After washing with water, dehydrating, and filtering, a diethyleneglycol ester plasticizer composition comprising 30 to 60 wt % of benzoicacid 2-{2-(2-ethylhexanoyloxy)-ethoxy} ethyl ester, 10 to 60 wt % of2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxyl}-ethyl ester, and5 to 40 wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy} ethyl ester isobtained.

The resultant diethylene glycol ester plasticizer composition can beused as plasticizer of a polyvinyl chloride resin to improve tensilestrength, elongation, hardness, transfer resistance, transparency,adhesivity, and/or compatibility of the resin.

The diethylene glycol ester based plasticizer composition of the presentinvention may also be used for other resins to improve tensile strength,elongation, transfer resistance, hardness, transparency, and/oradhesivity, and it is particularly suitable for a polyvinyl chlorideresin of a wrap film used for packing foods. It may also be used for apolyethylene based foaming sheet.

Thus, the present invention provides a polyvinyl chloride resin usingthe above-described diethylene glycol ester based plasticizercomposition.

The method of preparing the polyvinyl chloride resin is not particularlylimited. It can be prepared by the conventional method of copolymerizingpolyvinyl chloride with monomers copolymerizable with polyvinyl chlorideusing the plasticizer composition.

Hereinafter, the present invention is described in more detail throughexamples.

However, the following examples are only for the understanding of thepresent invention and they do not limit the present invention.

EXAMPLES Example 1

(1) Preparation of Diethylene Glycol Ester Plasticizer Composition

3 moles of diethylene glycol, 5.4 moles of 2-ethylhexanoic acid, 2.4moles of benzoic acid, 60 g of xylene as entrainer, and 2 g oftetraisopropyl titanate as catalyst, were put in a 2-L round flaskequipped with a stirrer and a condenser. The temperature was raised to220° C. and esterification was performed for 10 hours.

Unreacted acid was removed with a vacuum pump at 220° C. and 2 mmHg, andremaining acid was neutralized with 10 wt % of sodium hydroxide. Afterwashing with water and dehydrating, an absorbent was added. Theresultant solution was filtered to obtain a diethylene glycol estercomposition.

The diethylene glycol ester composition comprised 45 wt % of benzoicacid 2-{2-(2-ethylhexanoyloxy)-ethoxy} ethyl ester, 42 wt % of2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, 12wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy} ethyl ester, and 1 wt %of other unreacted materials. The composition and the content wereconfirmed with a gas chromatography mass spectrometer (GC-MS). The GC-MSresult is shown in FIG. 1.

(2) Preparation of Polyvinyl Chloride Resin Using Diethylene GlycolEster Plasticizer Composition

36 parts by weight of the diethylene glycol ester composition preparedin (1), 1.3 part by weight of a calcium-zinc stabilizer (KCZ-08, Kolon)and 12 parts by weight of epoxylated soybean oil (ShinDongBang) per 100parts by weight of a polyvinyl chloride resin (LS100S, LG Chem) werenixed and prepared sheet a thickness of 5-mm using a roll mill at 165°C. for 3 minutes. The sheet was pressed to a thickness of 1-mm. Thepressing conditions included preheating at 185° C. for 3 minutes,heating for 3 minutes, and cooling for 3 minutes. The resultant sheethaving a thickness of 1-mm was prepared into several type C dumbbellshaped samples.

(3) Physical Property Test of Polyvinyl Chloride Resin

Tensile strength, elongation, hardness, transfer resistance,transparency, and adhesivity were evaluated for the samples prepared in(2). The result is given in Table 1 below.

* Tensile strength: Tested according to ASTM D638 using a U.T.M. Thesample was pulled at a cross head speed of 500 mm/min. The site wherethe sample was cut was checked and the tensile strength was calculatedby the following equation.Tensile strength (kgf/mm²)=load (kgf)/(thickness (mm)×width(mm))  Equation [1]

* Elongation: Tested according to ASTM D638 using a U.T.M. The samplewas pulled at a cross head speed of 500 mm/min. The site where thesample was cut was checked and the elongation was calculated by thefollowing equation.Elongation (%)=(extension/initial strength)×100  Equation [2]

* Hardness: Hardness was tested at 5 sites for each sample to obtain themean value.

* Transfer resistance: The initial weight (W_(i)) of the sample wasweighed to the fourth decimal point. The sheet sample (3 cm z, 3 cm) wasinserted between polystyrene (PS) plates and put in an oven of 80° C.After letting for 48 hours under a load of 1 kg, the sample was takenout of the oven and kept in a constant temperature bath for at least 4hours. The weight (W_(o)) of the sample was weighed and the degree oftransfer was calculated by the following equation.Degree of transfer (%)=(W_(i)−W_(o))/W_(i)×100  Equation [3]

* Transparency: If the transparency was better than that of thedi-2-ethylhexyladipate (DEHA), a standard plasticizer, when observedwith naked eyes, the transparency was evaluated as superior. If thetransparency was comparable to that of DEHA, it was evaluated ascomparable, and if it was inferior to that of DEHA, it was evaluated asinferior.

* Adhesivity: If the adhesivity was better than that of DEHA, whentouched with a hands the adhesivity was evaluated as superior. If theadhesivity was comparable to that of DEHA, it was evaluated ascomparable, and if it was inferior to that of DEHA, it was evaluated asinferior.

Example 2

A diethylene glycol ester composition was prepared in the same manner ofExample 1, except for changing the composition and content as shown inTable 1. A polyvinyl chloride resin was prepared using the compositionas plasticizer. Tensile strength, elongation, hardness, transferresistance, transparency, and adhesivity were evaluated as in Example 1.The result is given in Table 1.

The diethylene glycol ester composition comprised 50 wt % of benzoicacid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, 24 wt % of2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, 24wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy}-ethyl ester, and 2 wt %of other unreacted materials. The composition and the content wereconfirmed with a gas chromatography mass spectrometer (GC-MS). The GC-MSresult is shown in FIG. 2.

Example 3

A diethylene glycol ester composition was prepared in the same manner ofExample 1, except for changing the composition and content as shown inTable 1. A polyvinyl chloride resin was prepared using the compositionas plasticizer. Tensile strength, elongation, hardness, transferresistance, transparency, and adhesivity were evaluated as in Example 1.The result is given in Table 1.

The diethylene glycol ester composition comprised 42 wt % of benzoicacid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, 12 wt % of2-ethylhexanoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, 44wt % of benzoic acid 2-{2-(benzoyloxy)-ethoxy} ethyl ester, and 2 wt %of other unreacted materials. The composition and the content wereconfirmed with a gas chromatography mass spectrometer (GC-MS).

The GC-MS result is shown in FIG. 3.

Comparative Example 1

A polyvinyl chloride resin was prepared in the same manner of Example 1,except for using di-2-ethylhexyladipate (DOA, LG Chem) instead ofdiethylene glycol ester of the present invention as plasticizer. Tensilestrength, elongation, hardness, transfer resistance, transparency, andadhesivity were evaluated. The result is given in Table 1.

Comparative Example 2

A polyvinyl chloride resin was prepared in the same manner of Example 1,except for using an ester based plasticizer prepared fromneopentylglycol and 2-ethylhexanoic acid instead of diethylene glycolester of the present invention as plasticizer. Tensile strength,elongation, hardness, transfer resistance, transparency, and adhesivitywere evaluated. The result is given in Table 1.

Comparative Example 3

A polyvinyl chloride resin was prepared in the same manner of Example 1,except for using an ester based plasticizer prepared from triethyleneglycol and 2-ethylhexanoic acid instead of diethylene glycol ester ofthe present invention as plasticizer. Tensile strength, elongation,hardness, transfer resistance, transparency, and adhesivity wereevaluated. The result is given in Table 1.

Comparative Example 4

A polyvinyl chloride resin was prepared in the same manner of Example 1,except for using diisonoyladipate (DINA, LG Chem) instead of diethyleneglycol ester of the present invention as plasticizer. Tensile strength,elongation, hardness, transfer resistance, transparency, and adhesivitywere evaluated. The result is given in Table 1. TABLE 1 ExampleComparative Example 1 2 3 1 2 3 4 Composition Diethylene 3(666) 3(666)  3(666) — — — — glycolmol (g) 2-Ethylhexanoic 5.4(1.296) 3.3(792)  2.1(504  — 3.1(744)   2.2(528)   — acidmol (g) Benzoic 2.4(446.4)3.3(613.8) 4.5(837) — — — — acidmol (g) Neopentylglycolmol (g) — — — —1.2(124.8) — — Triethyleneglycolmol (g) — — — — — 1(150) — Xylene (g) 6060 60 — 60 60 — Tetraisopropyl 2 2 2 — 1.5 2 — titanate (g) Tensilestrength 1.91 1.81 1.85 1.81 1.87 1.84 1.73 (kgf/mm²) — — — — — — —Elongation (%) 390 382 380 380 385 348 371 Transfer resistance (%) 1.952.21 3.22 0.2 0.2 0.3 0.1 Hardness (R-scale) 75 75 75 78 76 78 76Transparency Superior Superior Superior Standard Comparable InferiorComparable Adhesivity Superior Comparable Comparable Standard InferiorInferior Inferior

As seen in Table 1, the polyester resin using the diethylene glycolester composition of the present invention as plasticizer (Example 1)showed better tensile strength, elongation, transparency, and adhesivityand comparable hardness, compared with those prepared using the DOA(Comparative Example 1), the conventional plasticizer most widely usedin a wrap film for packing foods, the DINA (Comparative Example 4),which has the structure similar to that of DEHA, the standardplasticizer, the single-component plasticizer prepared fromneopentylglycol and 2-ethylhexanoic acid (Comparative Example 2) and thesingle-component plasticizer prepared from triethylene glycol and2-ethylhexanoic acid (Comparative Example 3). Thus, the plasticizer ofExample 1 is suitable for a plasticizer of a wrap film. To process awrap film, the transfer resistance should not be too high or too low.The plasticizer of Example 1 offers a suitable transfer resistance for awrap film.

And, the polyester resins using the diethylene glycol ester compositionsof Examples 2 and 3 as plasticizer have comparable, although notsignificantly superior, physical properties, compared with those ofComparative Examples. These physical properties are adequate for a wrapfilm. More importantly, they do not comprise phthalate, adipate, ortrimelitate compounds, which are known to generate environmentalhormones.

As described above, the diethylene glycol ester based plasticizercomposition of the present invention improves tensile strength,elongation, transfer resistance, hardness, transparency, adhesivity,and/or compatibility of a polyvinyl chloride resin without generatingenvironmental hormones, when employed as the plasticizer of the resin.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be male thereto withoutdeparting from the spirit and scope of the present invention as setforth in the appended claims.

1. A diethylene glycol ester compound for a plasticizer represented byFormula 1-1 below:R₁OCO—(CH₂)₂—O—(CH₂)₂—OCOR₂  (1-1)wherein R₁ is a phenyl group and R₂ isan alkyl group having 3 to 12 carbon atoms.
 2. The diethylene glycolester compound of claim 1, wherein the diethylene glycol ester comprisesbenzoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester.
 3. Thediethylene glycol ester compound of claim 2, wherein the benzoic acid2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester is prepared fromesterification of diethylene glycol, 2-ethylhexanoic acid, and benzoicacid.
 4. A diethylene glycol ester based plasticizer compositioncomprising a diethylene glycol ester compound represented by Formula1-1:R₁OCO—(CH₂)₂—O—(CH₂)₂—OCOR₂  (1-1)wherein R₁ is a phenyl group and R₂ isan alkyl group having 3 to 12 carbon atoms.
 5. The diethylene glycolester based plasticizer composition of claim 4, which further comprises:a diethylene glycol ester compound represented by Formula 1-2 below: anda diethylene glycol ester compound represented by Formula 1-3,R₃OCO—(CH₂)₂—O—(CH₂)₂—OCOR₄  (1-2) wherein each of R₃ and R4 is an alkylgroup having 3 to 12 carbon atoms; andR₅OCO—(CH₂)₂—O—(CH₂)₂—OCOR₆ (1-3) wherein each of R₅ and R6 is a phenylgroup.
 6. The diethylene glycol ester based plasticizer composition ofclaim 4, further comprising: (a) 10 to 80 wt % of the diethylene glycolester compound represented by Formula 1-1; (b) 5 to 80 wt % of thediethylene glycol ester compound represented by Formula 1-2; and (c) 5to 60 wt % of the diethylene glycol ester compound represented byFormula 1-3.
 7. The diethylene glycol ester based plasticizercomposition of claim 6, wherein: (a) the compound represented by Formula1-1 is benzoic acid 2-{2-(2-ethylhexanoyloxy)-ethoxy}-ethyl ester, (b)the compound represented by Formula 1-2 is 2-ethylhexanoic acid2-{2-(2-ethylhexanoyloxy) -ethoxy}-ethyl ester; and (c) the compoundrepresented by Formula 1-3 is benzoic acid2-{2-(benzoyloxy)-ethoxy}-ethyl ester.
 8. A method of preparing adiethylene glycol ester based plasticizer composition comprisingesterifying 10 to 40 wt % of diethylene glycol, 20 to 70 wt % of2-ethylhexanoic acid, 10 to 60 wt % of benzoic acid, 1 to 10 wt % ofxylene, and 0.01 to 1 wt % of tetraisopropyl titanate at 220° C. for 4to 10 hours.
 9. The preparing method of claim 8, wherein the compositioncomprises: (a) 10 to 80 wt % of the diethylene glycol ester compoundrepresented by Formula 1-1,R₁OCO—(CH₂)₂—O—(CH₂)₂—OCOR₂  (1-1); (b) 5 to 80 wt % of the diethyleneglycol ester compound represented by Formula 1-2,R₃OCO—(CH₂)₂—O—(CH₂)₂—OCOR₄  (1-2); and (c) 5 to 60 wt % of thediethylene glycol ester compound represented by Formula 1-3,R₅OCO—(CH₂)₂—O—(CH₂)₂—OCOR₆  (1-3).
 10. A polyvinyl chloride resinprepared using any one diethylene glycol ester based plasticizercomposition of claim.